Heat Transfer in Drop-Laden Turbulence

We investigate the heat transfer process in a multiphase turbulent system composed by a swarm of large and deformable drops and a continuous carrier phase. For a shear Reynolds number of Reτ=300, a constant dispersed phase volume fraction of Φ=5.4%, and a Weber number of We=3.0, we perform a campaign of direct numerical simulations (DNS) of turbulence coupled with a phase-field method and the energy equation. The Navier-Stokes equations are used to describe the flow field, while the phase-field method and the energy equation are used to describe the dispersed phase topology and the temperature field, respectively. We consider four Prandtl numbers, Pr=1,2,4 and 8, and we study the heat transfer process from warm drops to a colder turbulent flow. Using detailed statistics, we first characterize the time evolution of the temperature field in both the dispersed and carrier phase. We find that an increase of the Prandtl number, obtained via a decrease of the thermal diffusivity, leads to a slower heat transfer between the dispersed and carrier phase. Finally, we correlate the drop diameters and their average temperatures.